Illustrator's Effect > Stylize > Round Corners effect gives strange results on non-rectangles. How can you take an irregular shape that has sharp corners, for example:

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...and round the corners on each curved segment, like I've done manually on the first and last segments here?

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Things I've tried:

  • Doing it manually with the pen tool takes a very long time. It's difficult to make the rounding consistent or uniform, and it's very easy to accidentally distort the rest of the curves.
  • Effect > Stylize > Round Corners gives strange, inconsistent results:

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  • Inner strokes set to round corners seem to always come out square:

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4 Answers 4


Preface: I hesitate to post this as an answer because it requires third-party plug ins which are not free. However, free trial periods are available. So, it could solve a few problems before the trial period expires.

The easiest way I know to handle this is via VectorScribe by AstuteGraphics.com and their Dynamic Corners feature.

With Dynamic Corners you can set one corner (manually dragging or set a value), then hit a button to make all selected corners match. The difference is that there's a stop limit with Dynamic Corners. No corner will round so much it overlaps another rounded corner. The default Round Corners Effect in Illustrator doesn't do this. With the internal effect, overlapping rounded corners throw an error and either don't round at all or result in really, really odd shapes.

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An additional great thing about Dynamic Corners is the word "Dynamic". You can adjust all the rounding after the fact easily and visually rather than guessing and previewing like the standard effect demands.

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Other than manually adjusting each and every corner, this is the best method I am aware of.

With Illustrator's built in effect, it's all or nothing. With the rounded stroke method you can't control the amount of rounding, you essentially get the stroke rounding at whatever Adobe has determined it should be.

Disclaimer: I do not work for Astute Graphics and have no financial agreement with Astute Graphics. However, I have been granted access to plug-ins in exchange for my input. I've also purchased Astute Graphics' plug-ins myself beyond what may have been granted.


Here's the best I've found so far. Very open to better ideas.

  1. Set an inner stroke, equal to the radius you want your round corners to have.

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  1. Object > path > outline stroke
  2. In Pathfinder window, Exclude (cutting out overlaps). This effectively trims all shapes by the width of the stroke.
  3. Add an outer stroke equal to the original inner stroke, same colour as the fill.

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  1. (optional) Bake it into the path shapes with Object > path > outline stroke then pathfinder Unite

You wrote:

Illustrator's Effect > Stylize > Round Corners effect gives strange results on non-rectangles.

Seemingly true.

A workaround without flashy 3rd party tools is to make the roundings to rectangles and force them to make the curved shape later:

enter image description here

1.-3. A rectangle is splitted by subtracting smaller pieces with Pathfinder Panel > Minus Front. The result has got corner roundings and it's dragged to the brushes collection and defined to be a new art brush.

  1. A drawn arc

  2. The new brush is applied

  3. The stroke Width Tool is used to make the other end narrower


The best way to draw anything on illustrator knowing you are controlling what you want is by hand. Sure it takes more time but the final result will be what you want.

The image on this answer explain how to "easy" do rounded corners.

How to make rounded corners Its not automatic...no but that way you can control the little rectangles on your circle and make the curves be proportional with the big ones.

I hope it helps you... either way the fastest cheaper way is the one where you make the stroke and then delete it.

  • That's the technique I used to create the example in the question. The trouble with it is, there's no straightforward way to get what that answer calls segment "C" the same length each time, especially when the angles are different. Commented Dec 30, 2014 at 17:24

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